Establishing and running an effective telephone-based anticoagulation service

Impact of mobile health and telehealth technology on medication adherence of stroke patients: a systematic review and meta-analysis of randomized controlled trials

Background Stroke patients have low medication adherence after discharge, which leads to a high recurrence rate and poor disease control. Various strategies have been explored to enhance medication adherence in this patient population. Aim To evaluate the effects of mobile health (mHealth) and telehealth technology on medication adherence in stroke patients. Method All English studies that met the inclusion criteria published before September 2021 were obtained from PubMed, EMBASE, Web of Science, and Cochrane Library. Two researchers independently screened articles, extracted data, and evaluated the quality of the included studies. All articles were about randomized controlled trials. Medication adherence was used as the outcome index of this review. Random or fixed-effect models were used in statistical methods. I² statistics were used to evaluate heterogeneity. Results A total of ten studies met the inclusion criteria, covering 2151 stroke patients. Compared with the Usual Care group, the medication adherence scores of the mHealth technology group were better (standard mean deviation 0.67, 95% confidence interval, CI [0.49, 0.85], P < 0.001). The medication adherence ratio of the mHealth technology group was higher (odds ratio, OR, 2.81, 95% CI [1.35, 5.85], P = 0.006). Subgroup analysis showed that application and messaging interventions were more effective than the telephone call intervention (OR 4.05, 95% CI [2.10, 7.80], P < 0.001). The shorter the interval of the intervention, the better the medication adherence of patients (OR 4.24, 95% CI [2.30, 7.81], P < 0.001). Conclusion Compared with Usual Care, mHealth can effectively improve the medication adherence of stroke patients.

Evaluation of a Pharmacist-Led Remote Warfarin Management Model Using a Smartphone Application (Yixing) in Improving Patients' Knowledge and Outcomes of Anticoagulation Therapy

Background: The management of warfarin-treated patients has been recognized as a challenge due to narrow therapeutic range and food and drug interactions in warfarin therapy. We aim to evaluate the effect of a pharmacist-led remote warfarin management model using a smartphone application (app) on anticoagulation therapy.

Methods: Eligible patients who had received warfarin therapy after mechanical heart valve replacement were enrolled. The intervention group was offered a pharmacist-led remote warfarin management model using the app named Yixing. Yixing incorporates functions including automatic daily reminder, personal health record, educational program, and online counseling. The control group received traditional pharmacy services without Yixing. Co-primary outcomes were patients’ awareness score of warfarin therapy obtained from questionnaire, the medication adherence measured by the percentage of the correct-warfarin-taken days in the monitored period, the fraction of time in therapeutic range (FTTR), and the incidence of anticoagulation-related complications. The needed information of the patients was acquired via electronic medical records from the hospital, Yixing system and telephone follow-up when necessary.

Results: 64 and 66 patients were initially in the intervention and control groups respectively. After propensity score matching, 50 patients were assigned in each group. The intervention group had a median age of 51.0 years, in which 27 (54%) were male. The control group had a median age of 50.5 years, in which 28 (56%) were male. Patient awareness score in the intervention group was 8.00 (2.00), which was higher than that in the control group, with score at 6.50 (2.50) (p = 0.001). No significant difference was found in the percentage of the correct-warfarin-taken days between the two groups (p = 0.520). The median (interquartile range) value of FTTR was 80.3% (21.9%) and 72.1% (17.7%) in the intervention and control groups respectively (p = 0.033), and no significant differences in the incidence of anticoagulation-related complications were observed (p = 0.514).

Conclusion: The pharmacist-led remote warfarin management model using Yixing improves patients’ awareness of warfarin therapy and increases FTTR, but may not have significant improvements on medication adherence and safety.

The effect of reinforcing an educational programme using telephone follow-up on health-related quality of life of individuals using warfarin: A randomised controlled trial

OBJECTIVES

To evaluate the effect of reinforcing an educational programme through telephone follow-up on health-related quality of life and anxiety and depression symptoms in individuals starting warfarin therapy.

BACKGROUND

Educational interventions have improved quality of life in individuals using warfarin. Few studies have examined the addition of telephone follow-up to enhance educational interventions.

DESIGN

Randomised controlled trial in outpatient setting.

METHODS

Hospitalised adults starting warfarin therapy who agreed to participate received an educational programme about the warfarin treatment. At discharge, they were randomised to receive either five telephone follow-up calls (intervention) or no telephone calls (controls). Both groups were evaluated for health-related quality of life (using Duke Anticoagulation Satisfaction Scale) and symptoms of anxiety and depression (using Hospital Anxiety and Depression Scale) at three and six months post-discharge. Groups were compared at each time by independent-samples t test, and over time by repeated-measures analysis of variance, with time (three and six months), groups (intervention and control) and an interaction between time and group as factors. Level of significance was set at 0.05. The Consolidated Standards of Reporting Trials was used for reporting.

RESULTS

Fifty-two individuals (26 per group) completed the study. There were no statistical differences between groups in health-related quality of life, anxiety and depression symptoms, at both times post-discharge. Participants who received follow-up telephone calls reported better positive psychological impact (a subscale of quality of life) than controls.

CONCLUSIONS

Reinforcing an educational programme with telephone follow-ups did not have an overall effect on health-related quality of life of individuals using warfarin but promoted positive psychological impact.

RELEVANCE TO CLINICAL PRACTICE

The low cost of reinforcing educational programmes with telephone calls and the improvement in positive psychological aspects indicate that this type of intervention is still a promising intervention that could be further investigated and improved.

The effect of online versus hospital warfarin management on patient outcomes: a systematic review and meta-analysis

Background Patients using oral anticoagulants are prone both to thrombus from insufficient anticoagulant therapy and to bleeding by overmedication, so there is a need for further exploring. Aim of the review To assess the effect of online management (using electronic communication such as smartphone), and hospital management on the outcome of patients on long-term anticoagulant therapy, and to explore an appropriate anticoagulation management model. Method Studies published in English prior to July 2017 were retrieved from PubMed, EMBASE, Web of Science, and the Cochrane Library. Two researchers screened the literature independently, extracted the data and evaluated the methodological quality of the included studies. Meta-analysis was conducted using RevMan 5.3 software. The publication bias analysis was evaluated. Results A total of ten studies met the inclusion criteria, covering 16,915 patients. Of these, 8260 cases formed the online anticoagulation management group, and the other 8655 cases the hospital anticoagulant management group. There were no significant differences between the management models for time in therapeutic range, incidence of major or minor bleeding events, thromboembolic events, or warfarin-related emergency department visits. However, online management was associated with fewer warfarin-related hospital admissions than hospital management (odds ratio: 0.47, 95% confidence interval [0.30, 0.73]; P = 0.0009). Conclusion The online management of anticoagulant therapy was not inferior to hospital management, and may provide more convenient, higher quality anticoagulant therapy services for patients.

Educational and behavioural interventions for anticoagulant therapy in patients with atrial fibrillation

BACKGROUND

Current guidelines recommend oral anticoagulation therapy for patients with atrial fibrillation (AF) with one or more risk factors for stroke; however, anticoagulation control (time in therapeutic range (TTR)) with vitamin K antagonists (VKAs) is dependent on many factors. Educational and behavioural interventions may impact patients' ability to maintain their international normalised ratio (INR) control. This is an updated version of the original review first published in 2013.

OBJECTIVES

To evaluate the effects of educational and behavioural interventions for oral anticoagulation therapy (OAT) on TTR in patients with AF.

SEARCH METHODS

We updated searches from the previous review by searching the Cochrane Central Register of Controlled Trials (CENTRAL) and the Database of Abstracts of Reviews of Effects (DARE) in The Cochrane Library (January 2016, Issue 1), MEDLINE Ovid (1949 to February week 1 2016), EMBASE Classic + EMBASE Ovid (1980 to Week 7 2016), PsycINFO Ovid (1806 to Week 1 February 2016) and CINAHL Plus with Full Text EBSCO (1937 to 16/02/2016). We applied no language restrictions.

SELECTION CRITERIA

We included randomised controlled trials evaluating the effect of any educational and behavioural intervention compared with usual care, no intervention, or intervention in combination with other self-management techniques among adults with AF who were eligible for, or currently receiving, OAT.

DATA COLLECTION AND ANALYSIS

Two of the review authors independently selected studies and extracted data. Risk of bias was assessed using the Cochrane 'Risk of bias' tool. We included outcome data on TTR, decision conflict (patient's uncertainty in making health-related decisions), percentage of INRs in the therapeutic range, major bleeding, stroke and thromboembolic events, patient knowledge, patient satisfaction, quality of life (QoL), beliefs about medication, illness perceptions, and anxiety and depression. We pooled data for three outcomes - TTR, anxiety and depression, and decision conflict - and reported mean differences (MD). Where insufficient data were present to conduct a meta-analysis, we reported effect sizes and confidence intervals (CI) from the included studies. We evaluated the quality of evidence using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework.

MAIN RESULTS

Eleven trials with a total of 2246 AF patients (ranging from 14 to 712 by study) were included within the review. Studies included education, decision aids, and self-monitoring plus education interventions. The effect of self-monitoring plus education on TTR was uncertain compared with usual care (MD 6.31, 95% CI -5.63 to 18.25, I2 = 0%, 2 trials, 69 participants, very low-quality evidence). We found small but positive effects of education on anxiety (MD -0.62, 95% CI -1.21 to -0.04, I2 = 0%, 2 trials, 587 participants, low-quality evidence) and depression (MD -0.74, 95% CI -1.34 to -0.14, I2 = 0%, 2 trials, 587 participants, low-quality evidence) compared with usual care. The effect of decision aids on decision conflict favoured usual care (MD -0.1, 95% CI -0.17 to -0.02, I2 = 0%, 2 trials, 721 participants, low-quality evidence).

AUTHORS' CONCLUSIONS

This review demonstrates that there is insufficient evidence to draw definitive conclusions regarding the impact of educational or behavioural interventions on TTR in AF patients receiving OAT. Thus, more trials are needed to examine the impact of interventions on anticoagulation control in AF patients and the mechanisms by which they are successful. It is also important to explore the psychological implications for patients suffering from this long-term chronic condition.

Transition of stable patients from traditional anticoagulation clinic services to telephonic management

Background Outpatient warfarin dosing and monitoring with telephonic anticoagulation management (TAM) could be an effective alternative to other more labor intensive management models. Objectives To evaluate the time in therapeutic range (TTR) and number of extreme INR values (<1.5 or >4.5) of a telephonic system of warfarin management for stable patients who currently utilized traditional anticoagulation management services (AMSs). Method A retrospective, observational cohort with three groups (1) patients transitioned from an office-based anticoagulation clinic to TAM, (2) patients continuously enrolled in office-based AMS, (3) patients continuously managed by usual physician care without specialized anticoagulation services (UPC). Data was collected for six months before and six months after transition. Results All groups demonstrated decreased TTR from baseline to active phase, with the TAM and AMS groups showing similar magnitude of reduction (-10.61 and -12.66% respectively) but UPC group producing a greater drop (-20.08%). The TAM and AMS groups had similar rates of extreme INR levels; UPC had higher numbers of extreme INRs in three of the four measurements. Conclusion Stable patients transitioned from office-based anticoagulation clinic to a telephonic model of management performed equally as well as those who continued traditional enrollment.

Patient understanding of warfarin therapy: A review of education strategies

Significant research has been directed into defining best-practice anticoagulant management of thromboembolic events and optimal strategies for determining the safety and efficacy of therapy. Similarly, improved patient outcomes have been realised through the development of novel management strategies such as self-monitoring and self-management. Considerably, less energy has been directed towards developing and evaluating the best mechanisms for delivery of patient education. This is in spite of the fact that numerous confounders to stable therapy confront warfarinised patients on a daily basis. That patients requiring warfarin therapy should be educated with respect to that therapy has never been questioned. However, relatively little attention appears to have been paid to the development of robust models of patient education in the setting of oral anticoagulant therapy. This paper reviews the current literature with respect to warfarin education interventions before recommending strategies that may facilitate determination of the impact educating patients about warfarin therapy has upon clinical outcomes.

Educational and behavioural interventions for anticoagulant therapy in patients with atrial fibrillation

BACKGROUND

Current guidelines recommend oral anticoagulation therapy for patients with atrial fibrillation who are at moderate-to-high risk of stroke, however anticoagulation control (time in therapeutic range (TTR)) is dependent on many factors. Educational and behavioural interventions may impact on patients' ability to maintain their International Normalised Ratio (INR) control.

OBJECTIVES

To evaluate the effects on TTR of educational and behavioural interventions for oral anticoagulation therapy (OAT) in patients with atrial fibrillation (AF).

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) and the Database of Abstracts of Reviews of Effects (DARE) in The Cochrane Library (2012, Issue 7 of 12), MEDLINE Ovid (1950 to week 4 July 2012), EMBASE Classic + EMBASE Ovid (1947 to Week 31 2012), PsycINFO Ovid (1806 to 2012 week 5 July) on 8 August 2012 and CINAHL Plus with Full Text EBSCO (to August 2012) on 9 August 2012. We applied no language restrictions.

SELECTION CRITERIA

The primary outcome analysed was TTR. Secondary outcomes included decision conflict (patient's uncertainty in making health-related decisions), percentage of INRs in the therapeutic range, major bleeding, stroke and thromboembolic events, patient knowledge, patient satisfaction, quality of life (QoL), and anxiety.

DATA COLLECTION AND ANALYSIS

The two review authors independently extracted data. Where insufficient data were present to conduct a meta-analysis, effect sizes and confidence intervals (CIs) of the included studies were reported. Data were pooled for two outcomes, TTR and decision conflict.

MAIN RESULTS

Eight trials with a total of 1215 AF patients (number of AF participants included in the individual trials ranging from 14 to 434) were included within the review. Studies included education, decision aids, and self-monitoring plus education.For the primary outcome of TTR, data for the AF participants in two self-monitoring plus education trials were pooled and did not favour self-monitoring plus education or usual care in improving TTR, with a mean difference of 6.31 (95% CI -5.63 to 18.25). For the secondary outcome of decision conflict, data from two decision aid trials favoured usual care over the decision aid in terms of reducing decision conflict, with a mean difference of -0.1 (95% CI -0.2 to -0.02).

AUTHORS' CONCLUSIONS

This review demonstrated that there is insufficient evidence to draw definitive conclusions regarding the impact of educational or behavioural interventions on TTR in AF patients receiving OAT. Thus, more trials are needed to examine the impact of interventions on anticoagulation control in AF patients and the mechanisms by which they are successful. It is also important to explore the psychological implications for patients suffering from this long-term chronic condition.

Single-dose adjustment versus no adjustment of warfarin in stably anticoagulated patients with an occasional international normalized ratio (INR) out of range

BACKGROUND

Well-controlled patients on warfarin may still have occasional International Normalized Ratios (INRs) outside the therapeutic range. It is unclear whether there is any benefit of a single-dose correction in this situation.

AIM

To evaluate whether patients with very stable INR results should continue with the maintenance dose of warfarin without a single-dose correction, even when the result unexpectedly is moderately below or above the therapeutic range.

METHODS

A) We reviewed retrospectively 364 patients with unchanged maintenance dose for at least 6 months and an occasional INR outside the therapeutic range regarding decision on dosing and the effect on the next INR. B) We randomized 160 patients with at least 3 months of unchanged maintenance dose, an occasional INR deviating to a minimum of 1.5 or a maximum of 4.4 and unexplained or temporary, removable cause to a single-dose Change or No change. Follow-up INRs and telephone interviews were obtained after 2 weeks.

RESULTS

A) Retrospectively, the proportion of follow-up INRs outside the therapeutic range was 29.9% after No change, 27.1% after Increased dose and 25.7% after Skipped/reduced dose. However, the decision on No change was mainly taken in case of minimal INR deviations. B) Forty-eight (60%) of the patients randomized to Change were within the therapeutic range at follow-up versus 45 (56%) of those with No change, odds ratio 1.17 (95% confidence interval 0.59-2.30). For baseline INRs deviating down to 1.6 or up to 3.6 (therapeutic range, INR 2.0-3.0) the 2-week INRs did not differ between the groups.

CONCLUSION

Our results suggest only a small or no difference between the two managements of an occasional INR out of range in terms of the 2-week follow-up INR. In stable patients on warfarin with an occasional INR outside the therapeutic range it seems reasonable to continue with the same dose without a single-dose change and perform a repeat test in about 2 weeks. (ClinicalTrials.gov number, NCT00814177.).

Best strategies for patient education about anticoagulation with warfarin: a systematic review

Background

Patient education is an essential component in quality management of the anticoagulated patient. Because it is time consuming for clinicians and overwhelming for patients, education of the anticoagulated patient is often neglected. We surveyed the medical literature in order to identify the best patient education strategies.

Methods

Study Selection: Two reviewers independently searched the MEDLINE and Google Scholar databases (last search March 2007) using the terms "warfarin" or "anticoagulation", and "patient education". The initial search identified 206 citations, A total of 166 citations were excluded because patients were of pediatric age (4), the article was not related to patient education (48), did not contain original data or inadequate program description (141), was focused solely on patient self-testing (1), was a duplicate citation (3), the article was judged otherwise irrelevant (44), or no abstract was available (25).

Data Extraction: Clinical setting, study design, group size, content source, time and personnel involved, educational strategy and domains, measures of knowledge retention.

Results

Data Synthesis: A total of 32 articles were ultimately used for data extraction. Thirteen articles adequately described features of the educational strategy. Five programs used a nurse or pharmacist, 4 used a physician, and 2 studies used other personnel/vehicles (lay educators (1), videotapes (1)). The duration of the educational intervention ranged from 1 to 10 sessions. Patient group size most often averaged 3 to 5 patients but ranged from as low as 1 patient to as much as 11 patients. Although 12 articles offered information about education content, the wording and lack of detail in the description made it too difficult to accurately assign categories of education topics and to compare articles with one another. For the 17 articles that reported measures of patient knowledge, 5 of the 17 sites where the surveys were administered were located in anticoagulation clinics/centers. The number of questions ranged from as few as 4 to as many as 28, and questions were most often of multiple choice format. Three were self-administered, and 2 were completed over the telephone. Two reports described instruments along with formal testing of the validity and reliability of the instrument.

Conclusion

Published reports of patient education related to warfarin anticoagulation vary greatly in strategy, content, and patient testing. Prioritizing the educational domains, standardizing the educational content, and delivering the content more efficiently will be necessary to improve the quality of anticoagulation with warfarin.

Outcomes of Oral Anticoagulant Therapy Managed by Telephone vs In-Office Visits in an Anticoagulation Clinic Setting

BACKGROUND

Anticoagulation management by a dedicated anticoagulation clinic improves patient outcomes compared to routine medical care. Telephone-based anticoagulation management has been described but has not been compared to management with traditional office-based visits. The objective of this study was to compare warfarin-related monitoring outcomes, clinical end points, and the use of health-care resources as a result of warfarin-related complications in anticoagulation clinic patients whose management was conducted by telephone or in-office-based visits.

SETTING

Two university-affiliated anticoagulation clinics in Seattle, WA, and Chicago, IL.

METHODS

A retrospective, observational cohort design was used to investigate anticoagulation clinic patients who were managed by telephone encounters compared to those managed during face-to-face in-office encounters.

RESULTS

A total of 234 patients were evaluated; 117 patients managed by telephone were compared to 117 patients managed in office-based clinic visits. Monitoring outcomes (ie, time in therapeutic range and clinic visits per patient-year) were similar between groups. Differences in major bleeding (5.67% vs 5.62% per patient-year, respectively) and thromboembolic events (1.42% vs 2.81% per patient-year, respectively) between telephone-managed and face-to-face-managed patients did not reach statistical significance. The same was true for differences in the frequency of emergency department visits and hospital admissions to manage complications of warfarin therapy.

CONCLUSIONS

Telephone-based management of oral anticoagulation through a pharmacist-staffed anticoagulation clinic yielded clinical outcomes that were at least as favorable as those associated with traditional office-based visits. Telephone follow-up can be successfully used to manage warfarin therapy in patients who are unable to present in person to an anticoagulation clinic.

Pharmacy-managed anticoagulation: Assessment of in-hospital efficacy and evaluation of financial impact and community acceptance

BACKGROUND

The dangers of thrombosis are well known and yet current therapy presents a paradox; effective methods of pharmacological anticoagulation are available, but underemployed. The risks associated with the use of anticoagulants, especially warfarin, and the requirement of meticulous dosing with subsequent vigilant monitoring provides some explanation for this discrepancy. Efforts have been made to address this incongruity and increase anticoagulation treatment while mitigating complications; these include the development of dosing nomograms, patient self-monitoring of anticoagulation status, and increased pharmacist participation in anticoagulation management. Although the latter option has proven effective in outpatient clinics, its in-hospital application has received less attention. Therefore, our primary goal was to review the published literature to evaluate the efficacy of in-hospital, pharmacy-managed anticoagulation. In addition, our secondary goals were to assess the potential financial benefit and community acceptance of such pharmacist management.

METHODS

Potentially relevant studies were identified by searching PubMed; however, because some pharmacy journals are not included in this database, we also used internet search engines to locate articles. We subsequently employed the Science Citation Index to find additional papers that had referenced articles identified by our initial searches.

RESULTS

Several pilot studies, focusing primarily on adherence to warfarin dosing guidelines, found general equivalence between pharmacist and physician management and specifically illustrated the potential benefit gained simply through adherence to protocols. Nevertheless, these studies frequently lacked appropriate statistical analysis and examined small, and often heterogeneous, patient groups. Larger comparative studies also possessed some of the same flaws; however, taken together the equivalence and, in some cases improvement, in patient outcomes (e.g., greater control of International Normalized Ratios and decreased length of hospital stay) that they demonstrated suggest the value of increased pharmacist participation in anticoagulation therapy. Studies using heparin-based anticoagulation reported similar positive findings and hence support the warfarin results. Both published studies examining financial implications of in-hospital pharmacy management indicated potential for considerable savings. Finally, although we identified no in-hospital studies of community acceptance, positive survey results indicted that the majority of physicians and patients accepted pharmacy-managed outpatient anticoagulation.

CONCLUSIONS

The reported outcomes of pharmacy-managed in-hospital anticoagulation therapy appear at least equal, and sometimes superior, to those obtained through standard care; however, the lack of large well-designed trials prevents drawing definitive conclusions. Nevertheless, the continued and likely increased future need for anticoagulation in general and warfarin therapy in particular suggests that increased pharmacist involvement could enhance the quality of patient care.

Warfarin dose reduction vs watchful waiting for mild elevations in the international normalized ratio

BACKGROUND

Whether clinicians should decrease the warfarin dose in response to a mild, asymptomatic elevation in the international normalized ratio (INR) is unknown.

OBJECTIVES

The study objectives were as follows: (1) to evaluate the safety of an anticoagulation service (ACS) policy advocating that the warfarin dose not be changed for isolated, asymptomatic INRs of < or = 3.4; (2) to compare the dosing strategies of an ACS and primary care providers (PCPs); and (3) to quantify the relationship between reduction of the warfarin dose and the subsequent fall in the INR.

DESIGN AND SETTING

Randomized controlled study of health maintenance organization outpatients who were receiving warfarin.

PATIENTS

We identified 231 patients with a target INR of 2.5 and an isolated, asymptomatic INR between 3.2 and 3.4. Our ACS monitored 103 of the patients; PCPs monitored the remaining 128 patients.

MEASUREMENTS

From all 231 patients, we obtained INRs and warfarin dosing history. From the 103 ACS enrollees, we also recorded adverse events.

RESULTS

One ACS patient had epistaxis in the 30 days after the elevated INR. Twenty-three percent of ACS enrollees and 47% of PCP patients reduced their warfarin dose (p < 0.001). The median follow-up INRs were similar in both cohorts: 2.7 in the ACS enrollees and 2.6 in the PCP patients. However, in a subgroup analysis of 190 patients who presented with an INR of 3.2 or 3.3, ACS enrollees were more likely to have a follow-up INR in the range of 2 to 3 (p = 0.03). The median follow-up INR was 2.7 in 148 patients who maintained their warfarin dose, 2.5 in 77 patients who decreased their dose by 1 to 20%, and 1.7 in 6 patients who decreased their dose by 21 to 43% (p < 0.001).

CONCLUSIONS

These findings support maintaining the same warfarin dose in asymptomatic patients with an INR of < or = 3.3, and reducing the dose for patients who have a greater INR or an increased risk of hemorrhage. Warfarin dose reductions > 20% should be avoided for mildly elevated INRs.

Substitution of generic warfarin for Coumadin in an HMO setting

BACKGROUND

Substitution of generic warfarin for Coumadin presents safety concerns due to warfarin's narrow therapeutic index and because a prior generic formulation was removed from the US market after it was associated with adverse events.

OBJECTIVE

To determine whether a health maintenance organization (HMO) can add generic warfarin to its formulary without adversely affecting warfarin management or increasing adverse events.

DESIGN

In a prospective, observational study, an HMO that formerly dispensed only Coumadin added a generic warfarin preparation (Barr Laboratories, Pomona, NY) to its formulary.

SETTING

An anticoagulation service (ACS) affiliated with an HMO that was based in St. Louis, MO.

PARTICIPANTS

The cohort consisted of 182 enrollees in the ACS as of May 1, 1999. At the start of the study, these participants were taking Coumadin; by October 31, 2000, all had switched to Barr warfarin.

MEASUREMENTS AND MAIN RESULTS

We collected data 8 months prior to and 10 months after the introduction of generic warfarin for the following endpoints: international normalized ratio (INR) control, frequency of INR monitoring, number of dose changes, and rate of thrombotic and hemorrhagic events. Statistical process control charts were used to differentiate between random variation in the endpoints and changes due to different warfarin formulations, and we used the Wilcoxon signed-rank test to look for a change in any endpoint after patients changed to generic warfarin. No significant differences were found in any endpoint.

CONCLUSIONS

Substitution of Barr warfarin for Coumadin did not significantly affect INR control, warfarin management, or adverse events. Our findings suggest that HMOs can safely substitute at least 1 generic formulation of warfarin without extra monitoring.